The masks contain high concentrations of active ingredients to balance and purify the epidermis and preserve all the benefits of previous treatments performed. They contain Essential Fatty Acids to replenish the skin's proteo-lipidic film after exfoliation and to prepare the skin for the products that are applied during the treatment stage. Unlike other brands, at Biologique Recherche the masks are applied in the middle of the skin care program and not at the end. This is done deliberately to avoid removing the active ingredients used in the treatment stage when removing the mask.